Pituitary responsiveness to diurnal and nocturnal GnRH pulses in melatonin-treated ewe lambs

2000 ◽  
Vol 12 (2) ◽  
pp. 45 ◽  
Author(s):  
Sergio E. Recabarren ◽  
Alejandro Lobos ◽  
Emilio Cendoyya ◽  
Cristian Correa ◽  
Isolde Rudolph
Keyword(s):  
Luteinizing Hormone ◽  
Jugular Vein ◽  
Pulse Frequency ◽  
Ewe Lambs ◽  
Vein Catheter ◽  
High Responsiveness ◽  
Natural Photoperiod ◽  
Gonadotrophin Releasing Hormone ◽  
The Difference ◽  
And Control

It has been shown that oral administration of melatonin to Suffolk ewe lambs, from 10 weeks of age onwards, advances the onset of puberty compared with control lambs maintained under the same natural photope-riod. Luteinizing hormone (LH) pulse frequency at 20 and 26 weeks of age was unchanged by melatonin. However, LH pulse amplitudes greater than 1 ng mL –1 were consistently observed in melatonin-treated lambs, suggesting either a high responsiveness of the pituitary gland to endogenous gonadotrophin-releasing hormone (GnRH) pulses, or a large amount of GnRH released by each pulse. The purpose of the present study was to assess the pituitary responsiveness to six diurnal and six nocturnal exogenous pulses of GnRH (10 ng kg–1 bodyweight) in melatonin-treated ewe lambs (3 mg melatonin daily at 1600 hours, from 10 weeks of age; n = 5) and control lambs of the same age (n= 5), born in the spring and kept under natural photoperiod. Pulses of GnRH were given intravenously at 60-min intervals by means of an indwelling jugular catheter from 0900 to 1400 hours and from 2100 to 0200 hours to ewe lambs of 20 and 26 weeks of age. Blood samples were collected at 10-min intervals using a contralateral jugular vein catheter from 1 h before and up to 1 h after the last GnRH pulse. The difference (delta) between plasma LH concentrations at 0 min and the greatest concentration of LH after each GnRH pulse was calculated and compared in the same group. The total area under the GnRH response curve (AUC) was also calculated and compared within and between the groups. The AUC of melatonin-treated lambs (66.1 5.94 and 52.24 7.42 ng mL–1 /6 h, diurnal and nocturnal respectively) was greater than that of control lambs (39.42 4.29 and 32.82 3.6 ng mL –1 /6 h diurnal and nocturnal respectively; P<0.05) at 20 weeks of age. At 26 weeks of age, only the diurnal total AUC was greater in melatonin-treated lambs than in control lambs (60.17 7.98 and 29.8 5.02 ng mL –1 /6 h respectively; P<0.05). Delta LH concentrations in response to the first diurnal pulse of GnRH were greater than those in response to the fifth diurnal GnRH pulse (P<0.05) in melatonin-treated lambs of 20 weeks of age. Also, the delta LH concentrations in response to the first three diurnal GnRH pulses were greater than to the last three nocturnal pulses of GnRH (P<0.05). Delta LH concentrations were greater in response to the second diurnal pulse of GnRH than to the last three diurnal GnRH pulses, and greater than the responses to the first and the last four nocturnal GnRH pulses (P<0.05), at 26 weeks of age in melatonin-treated lambs. The response to nocturnal pulses of GnRH was similar. In control lambs, the responses to diurnal and nocturnal GnRH pulses were similar at 20 and 26 weeks of age. These results suggest that melatonin enhances the pituitary responsiveness to GnRH pulses in ewe lambs. Extra key words: luteinizing hormone, sheep.

Determinants of the annual pattern of reproduction in mature male Merino and Suffolk sheep: responses to a nutritional stimulus in the breeding and non-breeding seasons

2003 ◽  
Vol 15 (1) ◽  
pp. 1 ◽  
Author(s):  
Maria J. Hötzel ◽  
Stephen W. Walkden-Brown ◽  
James S. Fisher ◽  
Graeme B. Martin
Keyword(s):  
Luteinizing Hormone ◽  
Breeding Season ◽  
Follicle Stimulating Hormone ◽  
Hormone Secretion ◽  
Pulse Frequency ◽  
Mature Male ◽  
Scrotal Circumference ◽  
Gonadotrophin Secretion ◽  
Gonadotrophin Releasing Hormone ◽  
Breeding Seasons

This study was designed to test whether an acute improvement in diet would increase gonadotrophin secretion and testicular growth in strongly photoperiod-responsive Suffolk rams and weakly photoperiod-responsive Merino rams in both the breeding (February–March) and the non-breeding (July–August) seasons. Mature rams (n = 5 or 6) of these breeds were fed a maintenance diet (0.9 kg chaff + 100 g lupin grain) or the same diet supplemented with 1.5 kg lupin grain for 42 days in each season. Lupin grain is a rich source of both energy and protein. Testosterone, luteinizing hormone (LH) and follicle stimulating hormone (FSH) were measured in plasma from blood sampled every 20 min for 24 h on Days −1, 12 and 35 relative to the change in feeding. In rams supplemented with lupins, body mass increased in both breeds in both seasons (P < 0.001). Scrotal circumference and LH pulse frequency increased with lupin supplementation in both seasons (P < 0.003) in Merinos, but only during the breeding season (P < 0.003) in Suffolks. Plasma FSH concentrations were affected by diet only during the breeding season, being elevated on Day 12 in lupin-supplemented rams of both breeds (P < 0.05). It was concluded that Merino rams exhibit reproductive responses to improved nutrition irrespective of time of the year, whereas Suffolk rams respond to nutrition only when the hypothalamic reproductive centres are not inhibited by photoperiod. Thus, Suffolks do respond to nutrition, just as Merinos do, but only when photoperiod allows. This difference between breeds appears to be a result of differences in the neuroendocrine pathways that control pulsatile gonadotrophin-releasing hormone secretion.

Regulation of LH secretion during seasonal anestrus by dopaminergic pathways in Rasa Aragonesa ewes treated or not with melatonin

2003 ◽  
Vol 83 (2) ◽  
pp. 311-313 ◽  
Author(s):  
F. Forcada ◽  
J. A. Abecia ◽  
O. Zúñiga
Keyword(s):  
Luteinizing Hormone ◽  
Key Words ◽  
Dopaminergic System ◽  
Pulse Frequency ◽  
Steroid Dependent ◽  
Dependent Inhibition ◽  
And Control ◽  
Lh Secretion ◽  
Dopaminergic Pathways

The involvement of the dopaminergic system in the steroid-dependent inhibition of luteinizing hormone (LH) secretion during anestrus in ovariectomized, estradiol-implanted adult Rasa Aragonesa ewes was investigated in both ewes treated with melatonin on 8 March (n = 10) and in control (n = 8) ewes. Melatonin implants did not significantly increase LH secretion. However, treatment with pimozide induced a significant increase (P < 0.05) in LH pulse frequency in both groups during early anestrus. We conclude that, in the absence of males, the dopaminergic system is clearly involved in the inhibition of LH secretion during anestrus in both melatonin-treated and control ewes. Key words: Sheep, melatonin, pimozide

Effects of bovine follicular fluid on the secretion of LH and FSH in inhibin-immunized seasonally anoestrous ewes

1991 ◽  
Vol 128 (3) ◽  
pp. 403-410 ◽  
Author(s):  
P. G. Knight ◽  
J. H. M. Wrathall ◽  
R. G. Glencross ◽  
B. J. McLeod
Keyword(s):  
Follicular Fluid ◽  
Synthetic Peptide ◽  
Pulse Frequency ◽  
Α Subunit ◽  
Blood Samples ◽  
Gonadotrophin Secretion ◽  
Gonadotrophin Releasing Hormone ◽  
And Control ◽  
Lh Secretion ◽  
Dose Dependent

ABSTRACT It has been shown previously that treatment of seasonally anoestrous ewes with steroid-free bovine follicular fluid (FF), a crude inhibin-containing preparation, leads to a decrease in plasma FSH level which is accompanied by a marked increase in pulsatile LH secretion. Since FF contains several factors (e.g. activin, follistatin, unidentified components) other than inhibin, which might act to modify gonadotrophin secretion, it was of interest to establish whether these concurrent effects of FF on FSH and LH secretion persisted in ewes which had been actively immunized against a synthetic peptide replica of the α subunit of bovine inhibin. In June 1989 (anoestrous period) groups of inhibin-immune and control ewes (n = 5 per group) received 6-hourly s.c. injections of either bovine serum (2 ml) or one of two doses of FF (0·5 ml or 2 ml) for 3 days. Blood was withdrawn at 6-h intervals for 6 days beginning 24 h before the first injection. On the final day of treatment, additional blood samples were withdrawn at 15-min intervals for 8 h to monitor pulsatile LH secretion. Ewes were then challenged with exogenous gonadotrophin-releasing hormone (GnRH; 2 μg i.v. bolus) to assess pituitary responsiveness. In control ewes, FF promoted a dose-dependent suppression of basal (maximum suppression 65%; P < 0·01) and post-GnRH (maximum suppression 72%; P < 0·01) levels of FSH in plasma. This was accompanied by an increase (P < 0·01) in LH pulse frequency from 1·40±0·24 (s.e.m.) to 3·20±0·37 pulses/8 h. In contrast, FF did not affect secretion of either FSH or LH in inhibin-immunized ewes. However, mean plasma LH levels in immunized ewes were significantly lower (43%; P < 0·02) than in control ewes, irrespective of treatment. These findings indicate that in the anoestrous ewe the ability of FF to suppress plasma FSH is due entirely to its content of inhibin, that FF-induced enhancement of pulsatile LH secretion is mediated by inhibin, rather than some additional component of FF, and that immunoneutralization of endogenous inhibin can reduce LH secretion. Journal of Endocrinology (1991) 128, 403–410

STUDIES OF SEXUAL DIFFERENTIATION OF SHEEP

1978 ◽  
Vol 89 (1) ◽  
pp. 190-195 ◽  
Author(s):  
P. R. Wilson ◽  
M. F. Tarttelin
Keyword(s):  
Negative Feedback ◽  
Sexual Differentiation ◽  
Plasma Samples ◽  
Control Male ◽  
Male And Female ◽  
Ewe Lambs ◽  
Gonadotrophin Releasing Hormone ◽  
Gland Function ◽  
And Control ◽  
Lh Secretion

ABSTRACT Gonadotrophin releasing hormone (GnRH) (1 μg/kg was injected intravenously into pre-natally androgenised and untreated control ram and ewe lambs and castrated pre-natally androgenised rams on each of the 6th, 14th, 22nd and 30th week of post-natal life, and plasma samples collected at −20, −10, 0, 15, 30, 60, 90, 120 and 240 min from injection for LH estimation. No difference in pre-injection LH levels or responses to GnRH were observed between pre-natally androgenised and control male and female lambs. Castration resulted in significantly elevated pre-injection LH levels (P < 0.001) and responses to GnRH (P < 0.05). Forty-five week old control and pre-natally androgenised ewes were subjected to a GnRH injection and plasma sampling routine identical to that described above both before and 2 weeks after ovariectomy. Significantly elevated pre-injection LH levels and LH responses to GnRH (P < 0.001) resulted from ovariectomy but there were no differences in either parameter between control and androgenised ewes either before or after ovariectomy. It is concluded that since pre-natal androgenisation altered neither pituitary gonadotrophic activity nor pituitary or hypothalamic steroid negative feedback activity, the depressed basal LH secretion reported earlier in pre-natally androgenised lambs (Wilson & Tarttelin 1978) was probably due to impairment of hypothalamic production and/or release of endogenous GnRH rather than to modification of pituitary gland function.

Effect of the introduction of rams on the pulsatile release of luteinizing hormone and the onset of reproductive activity in ewe lambs

1991 ◽  
Vol 53 (2) ◽  
pp. 209-214 ◽  
Author(s):  
N. Z. N. Al-Mauly ◽  
M. J. Bryant ◽  
F. J. Cunningham
Keyword(s):  
Luteinizing Hormone ◽  
Sampling Period ◽  
Reproductive Activity ◽  
Pulse Frequency ◽  
Pulsatile Release ◽  
Ewe Lambs ◽  
The Mean ◽  
First Time ◽  
Lh Secretion

AbstractPre-pubertal ewe lambs were introduced to rams on 17 August (Tl), 12 September (T2) or 10 October (T3) or isolated from rams until 21 December (Tc) (no. = 13). Blood was taken for progesterone assay three times weekly (no. = 13) from 16 July. Blood was taken for LH assay at 15-min intervals for 8 h (no. = 8) at the time of the introduction of rams and subsequently at the time of further ram introductions. Blood was taken from Tc lambs at each ram introduction. Tl, T2 and T3 lambs ovulated for the first time 16 (s.e. 2·2) days earlier than Tc lambs but only T3 lambs ovulated after and apparently in response to the introduction of the rams. The mean baseline LH levels were higher in Tl, T2 and T3 lambs in comparison with Tc lambs at all sampling periods. The mean pulse frequency of LH secretion was significantly increased by the introduction of rams in T2 and T3 lambs in comparison with Tc lambs. The mean pulse frequency of LH secretion was greater in Tl, T2 and T3 lambs at the October sampling period in comparison to Tc lambs.

scholarly journals Kisspeptin Stimulates the Pulsatile Secretion of Luteinizing Hormone (LH) during Postpartum Anestrus in Ewes Undergoing Continuous and Restricted Suckling

Animals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2656
Author(s):  
José Manuel Hernández-Hernández ◽  
Graeme B. Martin ◽  
Carlos Miguel Becerril-Pérez ◽  
Arturo Pro-Martínez ◽  
César Cortez-Romero ◽  
...  
Keyword(s):  
Luteinizing Hormone ◽  
Jugular Vein ◽  
Pulse Frequency ◽  
Neural Pathways ◽  
Indwelling Catheter ◽  
Pulsatile Secretion ◽  
Intravenous Application ◽  
Access To Water ◽  
Ad Libitum ◽  
Lh Secretion

This study tested whether the intravenous application of kisspeptin can stimulate the pulsatile secretion of LH in suckling ewes during postpartum anestrus. Ten days after lambing, Pelibuey ewes were allocated among two groups: (1) continuous suckling (n = 8), where the lambs remained with their mothers; and (2) restricted suckling (n = 8), where the mothers suckled their lambs twice daily for 30 min. On Day 19 postpartum, the ewes were individually penned with ad libitum access to water and feed and given an indwelling catheter in each jugular vein. On Day 20, 4 mL of blood was sampled every 15 min from 08:00 to 20:00 h to determine LH pulse frequency. At 14:00 h, four ewes in each group received 120 μg of kisspeptin diluted in 3 mL of saline as a continuous infusion for 6 h; the remaining four ewes in each group received only saline. The interaction between kisspeptin and suckling type did not affect LH pulse frequency (p > 0.05). Before kisspeptin administration, pulse frequency was similar in all groups (1.50 ± 0.40 pulses per 6 h; p > 0.05). With the application of kisspeptin, pulse frequency increased to 3.50 ± 0.43 pulses per 6 h (p ≤ 0.014), so the concentration of LH (1.11 ± 0.14 ng mL−1) was greater in kisspeptin-treated ewes than in saline-treated ewes (0.724 ± 0.07 ng mL−1; p ≤ 0.040). The frequency of LH pulses was greater with restricted suckling than with continuous suckling (2.44 ± 0.29 versus 1.69 ± 0.29 pulses per 6 h; p ≤ 0.040). We conclude that intravenous application of kisspeptin increases the pulsatile secretion of LH in suckling ewes and that suckling might reduce kisspeptin neuronal activity, perhaps explaining the suppression of ovulation. Moreover, the effects of kisspeptin and suckling on pulsatile LH secretion appear to be independent, perhaps operating through different neural pathways.

Neurophysiological control of the secretion of gonadotrophin-releasing hormone and luteinizing hormone in the sheep--a review

1991 ◽  
Vol 3 (2) ◽  
pp. 137 ◽  
Author(s):  
JC Thiery ◽  
GB Martin
Keyword(s):  
Luteinizing Hormone ◽  
Steroid Receptors ◽  
Pulse Amplitude ◽  
Pulse Frequency ◽  
Neural Pathways ◽  
Releasing Hormone ◽  
Diagonal Band ◽  
Gonadotrophin Secretion ◽  
Gnrh Neurons ◽  
Gonadotrophin Releasing Hormone

The anterior pituitary gland secretes pulses of luteinizing hormone (LH) in response to pulses of gonadotrophin-releasing hormone (GnRH) released into the hypophysial portal blood by the hypothalamus. The pulsatile nature of the secretions is very important because the frequency of the pulses is directly related to the activity of the GnRH neurons. We can therefore take advantage of this phenomenon to develop mechanistic interpretations of responses to experimental treatments designed to unravel the neural pathways that influence what is, arguably, the most important individual signal controlling the activity of the reproductive system. We might also resolve the disagreements in the literature covering the neuropharmacology of gonadotrophin secretion. In this review, we describe work towards this end in the sheep. Most (95%) of the 2500 GnRH cell bodies in the sheep brain are located in a region covering the anterior hypothalamus, the medial preoptic area, the diagonal band of Broca, and the septum. The axons of up to 50% of these cells terminate in the organum vasculosum of the lamina terminalis. The remainder terminate in the median eminence and form the final common pathway for the many factors that affect gonadotrophin secretion. Among the factors known to affect the frequency of the pulses (or the activity of the GnRH neurons) are nutrition, pheromones, photoperiod and gonadal steroids (negative and positive feedback). Factors that affect GnRH pulse amplitude are more difficult to determine because variations in pituitary responsiveness prevent the use of LH patterns as a 'bioassay'. Techniques developed recently have allowed the direct measurement of GnRH pulse amplitude and revealed inhibitory effects of oestradiol, but we do not know whether this effect is due to a reduction in the amount of GnRH released by each neurone or a reduction in the number of neurones releasing a pulse. It is unlikely that the factors that alter pulse frequency do so by directly affecting the GnRH cells. For example, it is obvious that other cells, with specific receptors for pheromonal or nutritional stimuli, formulate a signal that is transferred to the GnRH cells via interneurones. Similarly, it is likely that a hypothalamic clock intervenes between photoperiodic inputs and GnRH output. Opioidergic neurons have been proposed as a link in this system, but the complexity of their action makes it unlikely that they directly affect the GnRH neurons. The responses to steroids are simple and rapid, but steroid receptors have not been found in GnRH cells, so at least one other set of interneurones is involved.(ABSTRACT TRUNCATED AT 400 WORDS)

Analysis of the horizontal structure of a measurement and control geodetic network based on entropy

2013 ◽  
Vol 62 (1) ◽  
pp. 23-31 ◽  
Author(s):  
Maria Mrówczyńska
Keyword(s):  
Geodetic Network ◽  
The State ◽  
Observation System ◽  
Optimum Number ◽  
Optimum Structure ◽  
Horizontal Structure ◽  
The Difference ◽  
And Control ◽  
Measurement And Control ◽  
Horizontal Displacements

Abstract The paper attempts to determine an optimum structure of a directional measurement and control network intended for investigating horizontal displacements. For this purpose it uses the notion of entropy as a logarithmical measure of probability of the state of a particular observation system. An optimum number of observations results from the difference of the entropy of the vector of parameters ΔHX̂ (x)corresponding to one extra observation. An increment of entropy interpreted as an increment of the amount of information about the state of the system determines the adoption or rejection of another extra observation to be carried out.

PENINGKATAN KEMANDIRIAN BELAJAR SISWA SMP MELALUI PEMBELAJARAN BERBASIS MASALAH

2019 ◽  
Vol 8 (2) ◽  
Author(s):  
Tanti Jumaisyaroh Siregar
Keyword(s):  
Problem Based Learning ◽  
Mathematic Teacher ◽  
Self Regulated Learning ◽  
Regulated Learning ◽  
Quasi Experimental ◽  
Independent Variable ◽  
Direct Learning ◽  
The Difference ◽  
And Control ◽  
Learning Data

The purposes of this research were to know: the difference of improvement in self-regulated learning of students that given problem-based learning with students that given  direct learning. The type of this research is a quasi-experimental research by taking samples from the existing population. The variable of this research consist of independent variable that is problem based learning model while the dependent variable isself regulated learning of student.The population of this research is all students of SMP Swasta Ar-rahman Percut and the sample of this research is grade eight with taken sample two classes (experiment and control)  with total 60 students. The instrument of this research were: scale of self-regulated learning. Data that have been collected then analyzed and performed hypothesis testing by using T-test. Based of the results analysis, it showed that: improvment  of the students’ self-regulated learning that given problem-based learning was higher than the students’ ability that given direct learning His then, suggested that problem-based learning be used as an alternative for mathematic teacher to improved students’ ability in mathematical critical thinking and self-regulated learning.

FINANCIAL CONTROLLING IN THE SYSTEM OF FINANCIAL MANAGEMENT

2018 ◽  
Vol 28 (1) ◽  
pp. 137-141
Author(s):  
Petya Yordanova – Dinova
Keyword(s):  
Comparative Analysis ◽  
Financial Management ◽  
Financial Stability ◽  
Business Environment ◽  
Innovative Approach ◽  
Financial Sustainability ◽  
The Common ◽  
The Difference ◽  
Effective Use ◽  
And Control

This paper explores the comparative analysis of the financial controlling, who is a result from the common controlling concept and the financial management. In the specialized literature, financial controlling is seen as an innovative approach to financial management. It is often presented as the most promising instrument of financial diagnostics. Generally speaking, financial controlling is seen as a process of managing the company`s assets which are valued in monetary measures. The difference between the financial management and the financial controlling is that the second covers all functions of management, analysis and control of finances, aiming at maximizing their effective use and increasing the value of the enterprise. Financial controlling is often seen as a function of the common practice of financial management. Its objective is to preserve the financial stability and financial sustainability of enterprises operating in a highly aggressive business environment.

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